Octane Mixing Calculator

How it is calculated

You enter the volume and octane rating of each of the two fuels. The volumes can be in any unit (litres, gallons) as long as both use the same one. The blend rating is the volume-weighted average: blend = (vol1 × octane1 + vol2 × octane2) ÷ (vol1 + vol2), and the total volume is vol1 + vol2. Both results are rounded to one decimal. A volume of 0 is accepted (the blend then equals the other fuel), but the two volumes cannot both be 0, a volume cannot be negative or empty, and each octane rating must be above zero and no higher than 130; a figure such as 870 typed by mistake gives no result. The octane figures must be on the same scale (for example both RON, or both AKI), because the tool simply averages the numbers you type. Real blends can deviate slightly from a straight average.

Common mistakes

• Mixing octane scales: averaging a RON figure (such as 95) with an AKI figure (such as 91) gives a meaningless number. Use the same scale for both fuels.
• Entering one volume in litres and the other in gallons. The weights are volumes, so both must use one unit.
• Leaving a volume empty instead of typing 0. An empty field gives no result at all.
• Typing an octane number with an extra digit (870 instead of 87). Anything above 130 gives no result.
• Counting the fuel already in the tank at the wrong amount. A tank showing a quarter full still holds a real volume, and that is the volume that belongs in the first field.